It is often necessary to quickly obtain a sample of blood and perform an analysis of the blood sample. One example of a need for obtaining a sample of blood is in connection with a blood glucose monitoring system, which a user must frequently use to monitor the user's blood glucose level.
Those who have irregular blood glucose concentration levels are medically required to regularly self-monitor their blood glucose concentration levels. An irregular blood glucose level can be brought on by a variety of reasons including illness such as diabetes. The purpose of monitoring the blood glucose concentration level is to determine the blood glucose concentration level and then to take corrective action, based upon whether the level is too high or too low, to bring the level back within a normal range. The failure to take corrective action can have serious implications. When blood glucose levels drop too low—a condition known as hypoglycemia—a person can become nervous, shaky and confused. That person's judgment may become impaired and that person may eventually pass out. A person can also become very ill if their blood glucose level becomes too high—a condition known as hyperglycemia. Both conditions, hypoglycemia and hyperglycemia, are potentially life-threatening emergencies.
One method of monitoring a person's blood glucose level is with a portable, hand-held blood glucose testing device. The portable nature of these devices enables users to conveniently test their blood glucose levels wherever the users may be. Typically, these devices can employ either electrochemical testing or colorimetric testing. In an electrochemical assay, a regent is designed to react with glucose in the blood to create an oxidation current at electrodes disposed within the reaction area. The current is directly proportional to the concentration of glucose in the user's blood. In a calorimetric assay, a reagent is designed to produce a colorimetric reaction indicative of a user's blood glucose concentration level. An optical instrument incorporated into the testing device then reads the colorimetric reaction.
Drawbacks associated with optical instruments for reading colorimetric reactions include size, low signal throughput and accuracy errors which are due, in part, to mechanical alignment (or mis-alignment) sensitivity of the optical components. These problems are further compounded when the optical instruments require readings at more than one wavelength. Providing multiple wavelengths compounds these problems because prior art devices produce light of each wavelength with a different light elements such as a light emitting diodes. It is difficult and expensive for multiple light emitting diodes to be aligned to provide identical illumination of the sample area. Misalignment and source geometry variations result in the light from each of the light emitting diodes having a different irradiances and different irradiance distributions across the sample. Thus, what is needed is a device than can illuminate a sample with a plurality of wavelengths of light, wherein each of the beams of light of different wavelengths have substantially uniform irradiances and irradiance distributions across the sample.